Writing in the fifth century the Spanish priest Orosius commented that ‘by the disposition of the land, Spain as a whole is a triangle and, surrounded as it is by the Ocean and the Tyrrhenian Sea, is almost an island’. That Nature should have endowed the Iberian Peninsula with such clearly marked boundaries has been taken by many to imply likewise that the political unity of the region was itself a natural and logical creation. But if, as Orosius noted, the boundaries of the peninsula are clear-cut, the physical landscape of the interior is far from being so. At the centre lies the vast arid tableland called the Meseta. Ringed by formidable mountain barriers, communications between this high plateau and the coastal regions of the peninsula are difficult, while the Meseta itself is bisected by a series of mountain ranges: the Sierra da Estrela, the Sierra de Gredos and the Sierra de Guadarrama. These physical divisions have endowed the peninsula with an astonishing regional diversity with the result that even if political unity has been frequently held up by some as a natural goal, Spain's ‘geographical handicap’, as Sánchez-Albornoz once referred to it, has in fact tended to encourage the development of regionalist and separatist movements.